Dental bridge and method of making same



arch 1938. c. w. KNOWLES DENTAL BRIDGE AND METHOD OF MAKING SAME Filed001;. 3, 1956' 6M EUMM ATTORNEY.

Patented Mar. 22, 1938 DENTAL BRIDGE 1 MAK ING AND METHOD OF SAME GalvinW. Knowles, San Francisco, Calif.

Application October 3,

5 Claims.

The present invention relates to dental bridges and a method of ,makingthe same. A dental bridgeis an artificial denture employed to fill thespace left by one or more extracted teeth and secured in placeinthemouth by attachment to the natural teeth on opposite sides of thespace to be filled by the bridgework.

It is an object of the present invention to provide an improved dentalbridge and improved means for securing in place such a bridge withoutgrinding away or in any way destroying or defacing any part of thenatural teeth to which the bridge is secured. j

Another object of the invention is to provide a bridge which may besecured in place by connection, with natural teeth without interferingwith the occluding surfaces of theteeth.

A further object is the provision of abridge formed in sections whichmay be firmly secured together and to the natural teeth without thenecessity of employing screws or other machined parts.

A further object of the invention is the provision of a sectional bridgeand means for securing the sections thereof together and to the naturalteeth, in which all parts of the bridge, including the securing meansthereof, are made by a casting or investment process from patterns takendirectly from the mouth, or models made from direct impressions.

A still further object of the invention is the provision of a novelmethod for forming the elements of a sectional bridge-and the member bywhich the sections thereof are secured together and to the teeth whichsupport the bridge.

Further objects and advantages of the invention will be made apparent inthe following specification, in which reference is made to theaccompanying drawing, wherein one form of the. invention is illustrated.

In the drawing- Fig. l is a perspective view of an assembled sectionalbridge constructed in accordance with my invention;

Fig. 2 is a plan view of the same bridge with the sections thereofseparated;

Fig. 3 Ba perspective view of one of sections of the bridge illustratedin Figs. 1 and 2;

Fig. 4 is an elevation of one of the major sec- ..tions of the bridge,ready to be placed in the position that it will occupy in the mouth;

Fig. 5 is a perspective view of a die which may be. used for forming adovetail, wedge-shaped slot in the wax pattern from which a major sec-,tion of the bridge ls-to be cast;

the major 1936, Serial No. 103,939

. Fig. 6 is a perspective view of a modified form of die employed whenthe two major castings are formed together and subsequently sawed apart;

Fig. 7 is a perspective view of a modified form of my invention, thesections of the bridge shown therein being shaped to receive and besecured together by a porcelain cap or crown; and

Fig. 8 is an elevation of one 'of the major sections of the bridge shownin Fig. 7 ready to be. placed in position in the mouth and also showingin cross section the porcelain crown to be used therewith.

V The bridge illustrated in the drawing comprises vertically andlongitudinallyseparate'd major sections it) and H secured together andto the supporting teeth by a double dovetail, wedge-shaped member l2.The central portions of the major sections l0 and II are relativelythick and combine, when drawn together by the wedge l2,

- to form an artificial tooth in the space between two naturalteeth,.indicated at l3 and M. The outer ends of the two major sectionsare in the form of thin, shell-like wings, cast to embrace closely thenatural teeth and support the central portion. The wings I5 and I6embrace the natural tooth l3, and the wings I! and I8 embrace thenatural tooth l4.

Complementary wedge-shaped recesses or slots [9 are formed in the twomajor sections of the bridge, and when these sections are placed inposition between the natural, supporting teeth I3 and Hi, the closelyfittingntapered wedge I2 is placed in these complementary slots andpressed firmly into the recess formed by the slots, thereby drawing thetwo major sections of the bridge together and producing a close fitbetween the separate sections and between their supporting wings and thenatural teeth 13 and 14. As the crown of the natural teeth, or thoseportions of the teeth which are visible above the gums, are somewhatrounded or protruding outwardly as they rise from the gums, and thewings are fitted closely to their exposed surfaces, this contactabsolutely prevents any shifting of the bridge, and makes it impossiblefor the bridge, after the sections thereof have been drawn together bythe wedge l2, to be moved either upwardly or downwardly relative to thesupporting teeth. The several parts of the bridge are additionallysecured to each other and sealed relative to the surfaces of the naturalteeth that they contact, by the use of any suitable dental cement,preferably of the class used for cementing in gold inlays and the like.The occluding surfaces of the natural teethare neither covered with thebridge structure nor in any way eifaced, so that their normal functionof mastication is not impaired.

In constructing a bridge according to the present invention, assumingthat there is a space between two natural, healthy teeth, and that it isindicated that bridgework is desirable, the natural teeth are firstscaled and polished to provide a clean, regular surface against whichthe cast portions of the bridgework may be closely fitted. A model ofthat portion of the denture to be occupied by the bridge, includingespecially the two natural teeth to which the bridge is to be anchored,and the surrounding gums, is then made in a plaster-like material by anyrecognized method of model-making, such, for example, as theplaster-impression method well known to the dental profession.

The model having been made, the work is outlined in wax which is applieddirectly to the model, or, in other words, patterns of the two majorsections of the bridge I and II are formed in wax against the model.During the forming of these wax patterns a die 20, such as illustratedin Fig. and which is formed of steel or other durable material, isplaced in the wax pattern so that upon removal it will leave therein arecess which is in its shape identical with the recess l9, which isformed in each of the major sections of the bridge. The use of this dieis preferred but not essential, as the recess may be carved or otherwiseformed in the wax if desired.

The completed wax patterns are then invested in any suitable investmentmaterial, and upon hardening of the investment material the wax isremoved, as is common practice, by boiling in water or applying heatdirectly to melt the wax and permit it to fiow from the investmentmaterial. The major sections of the bridge are then cast in gold or anyother material suitable for dental use, and the castings may be trimmedor polished before the bridge is finally assembled in the mouth.

When the castings are completed and removed from the investmentmaterial, they are placed in position on the model and an impression isthen taken, preferably in wax, of the recess in the central portion ofthe bridge which comprises the two wedge-shaped slots I 9. This waximpression is invested and a casting made, the same practice beingfollowed as though an inlay were being made for a cavity in a naturaltooth. The casting thus obtained, therefore, fits perfectly the doublewedge-shaped opening, and due to its tapered shape has a tendency, uponbeing inserted in said opening, to draw together the major sections ofthe bridge and cause them to fit perfectly about the outer walls of thenatural teeth which support the bridge structure. The occluding surfaceof the artificial tooth, which includes the top surface of the doubledovetail wedge I2, is shaped for proper registry with the other teeth inthe mouth, and the entire assembly is then placed in the mouth, cementbeing employed between all contacting surfaces of the major sections ofthe bridge, the wedge l2 and the supporting teeth l3 and I4.

Owing to the method of constructing the bridge that has been set forthabove, the castings fit the supporting teeth with the same precisionthat the ordinary, well-made inlay or crown possesses and the bridge isfirmly and permanently supported without danger of any harmful result'to the natural teeth. Furthermore, owing to the manner of constructionof this bridge, any imperfections in the nature of cavities or breaks ineither of the supporting teeth I3 or M may be repaired by the bridgestructure itself; that is to say, should a cavity exist in one or bothof the natural teeth to which the bridge is to be secured, the cavitymay be prepared prior to the taking of the impression from which themodel is made so that in forming the wax patterns from which the bridgesections are to be cast, an inlay will be formed as an integral part ofone of the bridge sections.

In placing the bridge in the mouth it is necessary to bring the twomajor sections thereof into position separately and from opposite sidesof the teeth to which they are to be secured, owing to the convexity of.the teeth which prevents the bridge from being slipped on or off afterit has been assembled. The wedge I2 is therefore inserted after themajor sections have been brought lnto place, and. by its interlockingconnection between these sections it insures against their becomingloosened or accidentally removed.

As an alternative to the method of forming the wax pattern in separatesections, as described above, the pattern may be made in a single pieceand thereafter cut into the separable sections Ill and I I. If thisprocedure is followed, it is preferable to use the double wedge-shapeddie 2| illustrated in Fig. 6, before the wax is separated for providingthe space in the wax pattern that is later to be occupied by the wedgeI2. The wedgeshaped members illustrated in Figs. 5 and 6 are providedwith relatively sharp, angular edges; but it is to be understood thatthe invention is not limited to the particular shape of these membersand that any suitable shape may be employed for forming an interlockand. a wedging action between the separable halves of the bridge.

The appearance of the bridge, as described above, may be enhanced by theuse, on the exposed surfaces thereof, of porcelain veneer which may beconstructed and applied by any well known method.

Figs. 7 and 8 illustrate a modification in which the major exposedportions of the central section of the bridge are of porcelain ratherthan gold, as is usually desired in dental work that is likely to befrequently exposed to view. In this modification, the separable sectionsl0 and I I of the bridge are of the same construction as that heretoforedescribed with the exception that the central portions of thesesections, instead of being shaped in the likeness of a tooth, are formedwith registering halves of a frusto-conical or tapered The pin 22 isshaped to be received within the identically shaped socket 23 formed ina porcelain cap or crown 24, illustrated in Fig. 8.

In assembling this modification with the bridge in the mouth, the twosections 10 and H thereof are brought together in their proper positionwith relation to the supporting teeth I 3 and I4, cement being appliedbetween the contacting surfaces of the sections and the surfaces ofcontact between the sections and the supporting teeth. The porcelaincrown 24 is then pressed into place over the registering halves of thepin 22, cement being employed to retain it in this position and thepressure applied being sufiicient to draw together the separable halvesof the bridge in much the same manner and with the same effect as isproduced by the use of the wedge 12 illus trated in Figs. 1 and 2.

In forming the wax pattern for tions of the bridge illustrated in thecentral portion of the pattern the metal por- Figs. 7 and 8, is firstroughly shaped to approximately the final form illustrated in Fig. 7;and with the wax in a pliable condition, the porcelain crown 24 ispressed into place to form for itself an exactly fitting seat in whichit Will eventually be received when the bridge is reproduced in gold.Care is taken in impressing this seat in the wax pattern that theoccluding surfaces of the porcelain crown are in a proper positionrelative to the other teeth in the mouth, and that the crown assumesthat position which it will eventually assume when secured to thefinished sections of the bridge.

While certain features of the invention are more or less specificallydescribed herein, it is to be understood that various changes may beresorted to in the construction of its several parts and the practice ofthe methods disclosed, within the scope of the appended claims.

Having described my invention, what I claim and desire to secure byLetters Patent is 1. A dental bridge comprising a pair of separablesections, each section having portions adapted to embrace natural teethfor support and having registering tapered slots formed therein, and adouble wedge member fitting within said registering slots to secure saidsections against separation.

2. The method of forming a dental bridge of separable sections having awedge-like member for securing them together which comprises castingsaid sections with a recess into which the wedge is to fit, and thentaking an impression of said recess and casting a wedge, using theimpression so taken as a pattern.

3. A dental bridge comprising a pair of separable sections, registeringextensions on said sections to form a tapered pin when the sections arebrought together, and a crown member having a tapered socket fittingover said pin.

4. A dental bridge comprising separable metal sections, a tapered pinformed one-half on each of said sections, and a porcelain crown having atapered socket fitting over said pin whereby the crown is supported andthe said sections are secured together.

5. A dental bridge comprising a pair of sections engageable withabutment teeth and separable on a plane disposed vertically andlongitudinally with respect to the abutment teeth, complementarywedge-like surfaces on said sections, and a member movable vertically insaid plane to engage said wedge-like surfaces and draw them. togetherand into close contact with the abutment teeth.

CALVIN W. KNOWLES.

